1. Field of the Invention.
The present invention relates generally to downhole shut-in tools, to methods using such shut-in tools, to various control systems therefor and related devices used therewith.
2. Description of the Prior Art.
Drawdown and buildup tests are often performed on production wells at regular intervals to monitor the performance of the producing formations in the well. A typical test setup usually includes a downhole closure valve, i.e. a shut-in valve, which is placed in the well and manipulated by slick line. There is usually a pressure recording gauge below the downhole shut-in valve which records the pressure response of the formation being tested as the valve is opened and closed. The formation is allowed to flow for a sufficient length of time to insure that it is drawn down to a desired level. After this drawdown period is complete, the shut-in valve is used to shut in the well. The formation pressure is allowed to buildup for a sufficient interval of time to allow it to reach a desired level, before another drawdown period is started. The entire process is then sometimes repeated immediately to acquire more pressure data from another drawdown/buildup test.
As mentioned, shut-in valves of the prior art have typically been actuated by mechanical means and particularly by means of mechanical actuators lowered on a slick line.